Auto Transmission Leak

for the mechanical types. '03 Acura MDX, all wheel drive. The car had a used tranny installed about 3 months ago, provided by my warranty company. We're not sure how many miles are on it; all the warranty company would say is it's less than the car's mileage (125k).

This weekend after a four hour drive I noticed drops of fluid- doesn't look like it's pouring out, but there was definitely some fluid in the snow. I put in two quarts of fluid on Saturday, and the fluid level seems to holding at the recommended level, according to the manual. While I was away, a tranmission mechanic recommended taking it apart and possibly replacing the torque converter, if necessary.  (Minimum $1k but close to $1500 if the converter had to be replaced).  He was basing this on the fact that there was a lot of fluid under the bottom of the car, but that was after the four hour drive and some local driving and losing the 2-3 quarts somehow,  which is why my local mechanic thought it was "probably safe" to drive home (stopping every hour to check the level, which was fine). Even after the drive home, the fluid level remains fine, but I still see a couple of drops under the car.  There is absolutely no slippage when driving- the only indication of trouble is the drip.  Gas mileage is same, shifting is same.

So I obviously need to find the source of the leak, but it takes hours (and hundreds of dollars) to drop and take apart the tran..  Looking for some ideas.  They sell sealants, but of course, the tran. guys don't recommend them.  Any ideas? I'm going to have the bottom of the car completely steam-cleaned and see if it's possible to see the source, maybe try one of those dyes, but I'm concerned with causing long-term damage.